Palestinians have insisted that the attack was carried out by far-right-wing Israeli nationalists in revenge for the murders of three Israeli teens. Israeli police had said they were exploring all possibilities, from an act by Jewish extremists to a Palestinian honor killing.

Palestinian Attorney General Muhammad Abd al-Ghani Uweili said Saturday that a preliminary autopsy of Abu Khdeir's body revealed that he had breathed in smoke – proof that he was alive when his body was set on fire.

Mohammed's cousin, a 15-year-old Palestinian-American, was injured during clashes with Israeli security forces last week. On Sunday, he was sentenced to nine days of house arrest, police spokeswoman Luba Samri said. Tariq Abu Khdeir, who lives in Florida but was visiting family here, will remain at a home in the east Jerusalem neighborhood of Beit Hanina.

Tariq's family says he was severely beaten by Israeli police during protests in Jerusalem last week. The incident is under investigation.

Suha Abu Khdeir, mother of Tariq Abu Khdeir, a U.S. citizen who goes to school in Tampa, shows a mobile phone photo of Tariq taken in a hospital after he was beaten and arrested by the Israeli police.(Photo: Mahmoud Illean, AP)

When the news of Sunday's arrests broke Sunday afternoon, Israelis took to social media to express shock and disgust that a fellow Jew could commit such a heinous crime.

"This is not our way, and the criminals who performed this heinous act brought disgrace upon the Jewish people and the state of Israel," Avalon said. "They must be brought to justice and prosecuted to the full extent of the law, as an example to others. Israel and the Jewish people's strength is based on the Jewish morals and values."

Jody Garfinkle, a Jerusalem mother of four told USA TODAY that "if these people are in fact the perpetrators of this horrible and inhuman crime they should be thrown in jail with no possibility of parole. Any person that would kill another human being and burn them to death is nothing other than a psychopath and does not belong in society."

Rahel Jaskow, a Jewish resident of Jerusalem, took a similar view. "Whoever they are, whatever their motive — if they are guilty, I wish them exactly the same thing I wish the killers of our own three boys: justice, swift and strong," Jaskow said. "If, in some parallel universe, I were the judge — Jewish or not — and the suspects were found guilty and were members of my own people, I would sentence them twice: once for the act itself, and a second time for dishonoring our people."

Prime Minister Benjamin Netanyahu said that Israel would act calmly and responsibly in the face of rising Israeli-Palestinian hostilities, just hours after Israel's military carried out airstrikes on 10 sites in Gaza.

The strikes killed seven Hamas members early Monday in the southern Gaza town of Rafah along the Egyptian border, the Islamist group told Reuters news agency.

The Israeli airstrikes targeted what the army said were militant sites including rocket launchers and a weapons manufacturing site, following at least 29 other rockets and mortar shells fired from the Gaza Strip at Israel over the weekend.

Two of those rockets were aimed at Beersheba, a southern city deeper into Israel than any other attack in the current round of violence. The military said its "Iron Dome" defense system intercepted the two rockets.

An Iron Dome air defense system fires to intercept a rocket from Gaza Strip in the costal city of Ashkelon, Israel, on July 5.(Photo: Tsafrir Abayov, AP)

Tensions have been high since the three Israeli teens were abducted on June 12. The Israelis blamed Hamas for their killings and launched a major crackdown against the Islamic militant group.

Protests spread over the weekend from Jerusalem to Arab towns in northern Israel, with hundreds of people throwing rocks and fire bombs at officers who responded with tear gas and stun grenades, according to Israeli police. Samri said 22 Arab Israelis were arrested in clashes on Saturday.

Israeli Arabs, unlike Palestinians in the West Bank and Gaza, hold citizenship rights. But they often face discrimination and many identify with the Palestinians. Even so, violent riots like those that occurred on Saturday are rare.

Clashes mostly subsided by early Sunday, but the situation remained tense. Samri said a Jewish woman was attacked and lightly wounded early Sunday by a group of Palestinians in Jerusalem's Old City. Her husband fired his weapon and the attackers fled, and police were searching for them, Samri said.

Tariq's parents, Suha and Salah, said Tariq was the last person with Mohammed shortly before he was seized. They said Tariq left Mohammed to eat before the Ramadan fast began at dawn Wednesday.

Police said Tariq resisted arrest, attacked officers, and was captured with a slingshot for lobbing stones.

His face was masked in a keffiyeh, an Arab headscarf that some Palestinian protesters wore during the clashes to conceal their identity, police added. He was detained along with six other protesters, police said, including some armed with knives, adding that several officers were hurt in that specific protest, one of many that day.

Amateur video of what Tariq's father, Salah, said was the beating aired on a local television station, and he said he could recognize his son from his clothing.

The U.S. State Department said it was "profoundly troubled" by reports of his beating and demanded an investigation. Israel's Justice Ministry quickly launched a formal investigation.

Ron Dermer, the Israeli ambassador to the U.S., said Sunday, "It's unacceptable in our system if police use excessive force."

He told Fox News Sunday that the teen was "not just an innocent bystander who was pulled off a schoolyard. He was with six other people. They were masked. They threw petrol bombs and Molotov cocktails at our police. Three of them had knives, from what I understand. That does not excuse any excessive use of force, and our justice ministry is opening an investigation."

In the West Bank, the army arrested a Palestinian in the city of Hebron. His family identified him as Hossam Dufesh. The army would not elaborate on the arrest, but Israeli forces have concentrated its search for the killers of three Israeli teens in the Hebron area.

Contributing: John Bacon, USA TODAY; the Associated Press

Palestinians celebrate the announcement of a cease-fire on Aug. 26 in Gaza City. Palestinian President Mahmoud Abbas announced an Egyptian-brokered cease-fire proposal to end seven weeks of fighting between Israel and militant groups in the Gaza Strip. (Photo: Mohammed Saber, European Pressphoto Agency)

A worker removes debris from the Cohen family bedroom after a missile fired by militants in the Gaza Strip made a direct hit in their home in Ashkelon, Israel. (Photo: Abir Sultan, European Pressphoto Agency)

A Palestinian boy walks across the rubble of a house belonging to the al-Dakhani family after an Israeli airstrike on the Rafah refugee camp, southern Gaza Strip. Two people were wounded in the attack. (Photo: Eyad Baba, AP)

A man looks out the window of a damaged classroom after a rocket, fired by Palestinian militants from the Gaza Strip, landed in the courtyard of a kindergarten in Ashdod, Israel. (Photo: Jack Guez, AFP/Getty Images)

A Palestinian man sweeps the floor of his home that was damaged after a mosque across the street was hit by an Israeli airstrike in Beit Lahia in the northern Gaza Strip. (Photo: Roberto Schmidt, AFP/Getty Images)

A Palestinian woman watches from a hole in a home belonging to Hamas financial official Mohammed al-Ghul after it was targeted by an Israeli airstrike in Gaza City. One of several targeted airstrikes by Israeli forces killed Al-Ghul in his vehicle. (Photo: Mohammed Abed, AFP/Getty Images)

Relatives and close family friends of Daniel Turgeman touch his coffin during the boy's funeral on Aug. 24 in Yevul, Israel. Turgeman, 4, was killed in a mortar attack fired by Palestinians inside the Gaza Strip on Aug. 22. (Photo: Jim Hollander, European Pressphoto Agency)

An Israeli firefighter extinguishes a fire after rockets fired by Palestinian militants from the Gaza Strip hit a field near the southern Israeli city of Sderot. (Photo: Menahem Kahana, AFP/Getty Images)

Palestinians carry the body of the wife of Mohammed Deif, Israel's most-wanted man, at the Jabaliya refugee camp in the northern Gaza Strip. According to media reports, Deif's wife and son were killed Aug. 20 in an Israeli airstrike on Gaza City. Israel holds Deif, the leader of the Qassam Brigades, Hamas' military wing, accountable for directing the Gaza conflict from underground. (Photo: Mohammed Saber, European Pressphoto Agency)

Israeli soldiers in an undisclosed southern Israeli location take cover inside a cement pipe near the border with the Gaza Strip as a 'red alert' sounds, signaling that Palestinian militants have fired a rocket toward the area. The Israeli army reported that Palestinians shot about 180 rockets and mortars since the collapse of the cease-fire, with scores of Israeli strikes inside the Gaza Strip. (Photo: Avi Roccah, European Pressphoto Agency)

Palestinians grieve over the death of Widad Mustafa Deif, 27, and her 8-month-old son, Ali Mohammed Deif, during their funeral in Jabaliya refugee camp. They were killed by an Israeli strike Aug. 20. (Photo: Khalil Hamra, AP)

A Palestinian boy spots two Israeli drones in the late afternoon Aug. 19. Palestinians fled their homes in neighborhoods of eastern Gaza City carrying bags of clothes, pillows and mattresses after renewed Israeli airstrikes, witnesses said. Nine days of relative quiet in the skies over Gaza came to an abrupt halt when rockets struck Israel just hours before the truce was to expire at midnight local time. Israel immediately ordered a military response, with warplanes striking targets across the coastal strip. (Photo: Roberto Schmidt, AFP/Getty Images)

A rocket fired by Palestinian militants inside the Gaza Strip rises into the night sky. More than 50 rockets were fired toward Israeli civilian centers from Gaza on Aug. 19, shattering the 24-hour cease-fire, and Israel responded with multiple air force attacks on Gaza, with deaths and many casualties reported. (Photo: Avi Roccah, European Pressphoto Agency)

Palestinian rescuers clear the rubble of a destroyed house following an Israeli airstrike in Gaza City. The Israeli airstrike killed a young girl and a woman, wounding 16 other people. (Photo: Mohammed Abed, AFP/Getty Images)

An Egyptian soldier stands guard on the Egyptian side of the border between Egypt and the Gaza Strip on Aug. 13, overlooking the damage in Rafah caused by a month of fighting between the Israeli military and Hamas militants. (Photo: Said Khatib, AFP/Getty Images)

Palestinian mourners carry the body of Zakariah al-Aqrah, 21, during his funeral in the West Bank village of Qabalan. The Israeli military said it killed al-Aqrah early Monday morning after he opened fire on an Israeli force that had come to arrest him in connection with shootings targeting Israeli soldiers two weeks ago. (Photo: Majdi Mohammed, AP)

A Palestinian man standing in a crowd of onlookers reacts to watching a soap factory go up in flames moments after it was hit by an Israeli airstrike in Gaza City, Aug, 10. (Photo: Roberto Schmidt, AFP/Getty Images)